The simian virus 40 (SV40) late promoter can be trans-activated by SV40 T-antigen in the absence of DNA replication. Transfection experiments suggest that T-antigen trans-activation may involve either direct promoter binding or induction of one or more cellular transcription factors. In collaboration with Dr. Peter Tegtmeyer, we have demonstrated a role for T-antigen binding site I, as well as II, in the T-antigen binding dependent pathway. To gain further understanding of the mechanisms by which trans- acting factors interact to recognize transcriptional regulatory sequences, we have examined the ability of SV40 T-antigen and adenovirus E1A protein to stimulate the adenovirus E2 promoter. Chemically synthesized mutants of the E2 promoter function as an inducible enhancer. by insertion of 5, 10, 15 or 20 base pairs of non-specific DNA between inverted repeats in the E2 enhancer, we have found that a specific spatial arrangement of sequences on the E2 promoter are required for trans-activation.